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Amana Heat Pump Groaning at Startup

I have a AVPTC31371 indoor in the attic of my 2 story house connected to a asx140241 outdoor heatpump condensor. When the temp drops below approx 32 degrees the unit groans and vibrates the house for the first 5 to 10 seconds when it starts. It then quiets down and runs normal. Doesn't seem to do it when the temp is 35 degrees and higher.

I have anther duplicated set on the first floor and both of these were installed in October. The first floor unit is quiet even on start up.

I am lost and need some advice. The company that installed the system says this is normal.

It wakes everyone up at night when it comes on....this cannot be "normal"

I would check to see if there is a crankcase heater and if its working. The refrigerant should also be checked. Sounds like what is called flooded starting. If there is a long line set there may need to be a liquid line shut off valve to help control the refrigerant on the off cycle.

Groaning at startup

Originally Posted by coolinman

I would check to see if there is a crankcase heater and if its working. The refrigerant should also be checked. Sounds like what is called flooded starting. If there is a long line set there may need to be a liquid line shut off valve to help control the refrigerant on the off cycle.

The easy way to check is with the outdoor unit not running check for current flow on the high voltage supplying the unit. This is not fool proof there may be a thermostat to turn it off when not need to improve the efficency. You should be able to trace it out on the wiring diagram if you need to. The heater probably operates at around 50-60 watts so thats about .25 amps at 240 VAC. The reason its there is because the manufacture knows its needed and would cause problems at low ambient operation without it. If there is no current the heater and thermostat can be checked with a electrical meter.
Good Luck !

Line Shut Off Valve

Originally Posted by coolinman

I would check to see if there is a crankcase heater and if its working. The refrigerant should also be checked. Sounds like what is called flooded starting. If there is a long line set there may need to be a liquid line shut off valve to help control the refrigerant on the off cycle.

Would a liquid line shutoff valve work on a heat pump. Doesn't the refrigerant have to travel both ways in a heat pump? Not sure but wanted to know before I inquired about having one installed?

Would a liquid line shutoff valve work on a heat pump. Doesn't the refrigerant have to travel both ways in a heat pump? Not sure but wanted to know before I inquired about having one installed?

Yes you are correct you will need a special biflow valve installed. Does your indoor unit have a txv?

The biflow valves cannot shut tight in the reverse flow direction.

So make sure valve is installed with reverse flow is cooling. They can also make some strange noises for a min or two after shut down. The noise goes away if there is a hard shut off txv on indoor coil.

txv valves

Originally Posted by SBKold

Yes you are correct you will need a special biflow valve installed. Does your indoor unit have a txv?

The biflow valves cannot shut tight in the reverse flow direction.

So make sure valve is installed with reverse flow is cooling. They can also make some strange noises for a min or two after shut down. The noise goes away if there is a hard shut off txv on indoor coil.

An easier upgrade may be hard shutoff txv installed in outdoor unit.

I checked specs on the indoor unit and it does have a thermal expansion valve. The noise is definitely upon startup of the condenser it vibrates ingrowns for about 10 seconds and then quiets down

More Info

Here is what I have determined. If the unit shuts off and is only off for 10 or 15 minutes, it will make the noise on start up. If it can sit longer in off mode it will start quietly. Another AC guy told me he believes that there is a valve shutting and not allowing the pressures to equalize, but when the unit is off longer it has time to do so. Not sure what this means but it follows this pattern. If I can keep the compressor off for a longer period it is quiet when it starts. What I have noticed is when it is cold outside the thermostat will come on in 10-15 minutes after shutting off. I talked with Honeywell, they said the thermostat will switch on when the temp drops 1 degree from the set temp and there is no changing this. Seems like it would make a unit run short cycles if this is the way is works. Any input?